Discrete element modeling of a vibratory subsoiler

Discrete Element Modeling of a Vibratory Subsoiler J. van der Linde Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa. Thesis: MScEng (Mech) December 2007 Vibrating a tillage tool is an e ective way of reducing the draft force required to pull it through the soil. The degree of draft force reduction is dependent on the combination of operating parameters and soil conditions. It is thus necessary to optimize the vibratory implement for di erent conditions. Numerical modelling is more exible than experimental testing and analytical models, and less costly than experimental testing. The Discrete Element Method (DEM) was speci cally developed for granular materials such as soils and can be used to model a vibrating tillage tool for its design and optimization. The goal was thus to evaluate the ability of DEM to model a vibratory subsoiler and to investigate the cause of the draft force reduction. The DEM model was evaluated against data obtained from eld testing done with a full scale single tine vibratory subsoiler. Soil testing was also done for material characterization and for the calibration of DEM material properties. The subsoiler was simulated using a commercial code, PFC3D. The e ect on the simulation results of particle diameter, di erent bonding models and damping models was investigated. The nal simulations were evaluated against the experimental results in terms of the draft force and material behaviour. The cause of the draft force reduction due to vibration was also investigated with the aid of the DEM model. From the results it was concluded that DEM is able to model the vibratory subsoiler for its design and optimization. The DEM model also provided valuable insight into the cause of the draft force reduction such as the increased peak stresses due to vibration and the increase in particle kinetic energy.